It is conventional to synthesize ammonia by the Haber-Bosch process developed in the mid-twentieth century. The Haber-Bosch ammonia synthesis is accomplished by the reaction of nitrogen and hydrogen at 700° C. and requires 700 atmospheres to achieve good yields. This exothermic reaction releases heat, which must be removed from the reaction facility. Due to low conversion efficiency per pass, hydrogen and nitrogen must be recycled and ammonia removed by condensation at high pressures. Nitrogen is prepared by combustion of the oxygen from air to leave CO2 and water vapor; the heat of combustion is used for thermal decomposition of methane.
Numerous patents discuss ammonia synthesis from nitrogen including:
U.S. Pat. No. 4,142,993 which deals only with an improved Haber process, using an improved doped carbon catalyst; for ammonia synthesis;
U.S. Pat. No. 4,180,552 to Graham, et al. again discloses an improved Haber process, which involves hydrogen recovery from ammonia synthesis in which purging streams are recycled to the reaction zone to improve ammonia yields.
U.S. Pat. No. 4,180,553 to Null, et al. again also discloses an improved Haber process, which involves hydrogen recovery from ammonia synthesis in which purging streams are recycled to the reaction zone;
U.S. Pat. No. 4,390,509 to Weston, et al. in which synthesis gas is used to produce ammonia and digestion of phosphate rock and eventually ammonium phosphate;
U.S. Pat. No. 4,891,262 to Lichtin, et al. produces ammonia by catalyzed reduction of nitrogen absent photo energy;
U.S. Pat. No. 4,938,855 to Lichtin, et al. produces ammonia by photo promoted catalyzed reduction of nitrogen; and,
U.S. Pat. No. 4,981,669 to Pinto produces ammonia synthesis gas from natural gas by several reforming steps involving the water reforming shift process by adjusting the temperature of the reforming tubes and the air fed to the secondary reformer stage.
Hydrogen can be prepared from natural gas by water reforming or thermal decomposition. Water reforming is most often used because it is exothermic, and thus requires no energy input. Thermal decomposition is not often used because it requires energy input. In thermal decomposition, refractories are heated and natural gas is flowed over them; in the process of the endothermic decomposition the refractories cool and must be reheated. For this reason this process is not often used, as discussed in the McGraw-Hill Encyclopedia of Science and Technology 8th Ed., 1997, “Carbon Black” p. 234–235. To be cost effective the thermal decomposition process must be combined with some process or processes that release heat. With catalysts the thermal decomposition process can be made to operate at 700° C. This process is sometimes called the Bosch process
Numerous patents discuss hydrogen synthesis in which hydrogen, if desired, can be reacted with nitrogen to produce ammonia including:
U.S. Pat. No. 4,836,898 to Noyes discusses high temperature conversion of methane to hydrogen and carbon;
U.S. Pat. No. 5,266,175 to Murphy and U.S. Pat. No. 5,411,649 to Roussey, et al. are concerned with conversion of a methane feed to hydrogen by microwave radiation in an electromagnetic field;
U.S. Pat. No. 6,002,059 to Hellring, et al. is concerned with the upgrading of natural gas into higher order hydrocarbons;
U.S. Pat. No. 6,245,309 B1 to Etievant, et al. discloses a hydrogen generator from fuel gas having a chamber provided with means for maintaining a predetermined temperature and electrical discharges at a reduced current level; and,
U.S. Pat. No. 6,293,979 B1 to Choudhary, et al. catalytically converts natural gas to synthesis gas.
It is also known to use the exothermic energy from a reaction in one area of a plant to provide energy to facilitate the reaction of endothermic reaction in another area of the plant. Numerous patents discuss such utilization including:
U.S. Pat. No. 6,002,059 to Hellring, et al. are concerned with the upgrading of natural gas into higher order hydrocarbons discloses the concept of balancing the heat requirements of the several steps by transferring energy from the exothermic reactions to the endothermic (see col. 7 lines 1–30).
U.S. Pat. No. 6,228,341 B1 to Hebert, et al. also involves the transfer of energy from the exothermic reaction area to the reaction streams by indirect heat exchange through heat exchange channels.
U.S. Pat. No. 6,245,309 B1 to Etievant, et al. discloses a hydrogen generator from fuel gas having a chamber provided with means for maintaining a predetermined temperature and electrical discharges at a reduced current level.
U.S. Pat. No. 6,293,979 B1 to Choudhary, et al. catalytically converts natural gas to synthesis gas by a technique where the exothermic oxidative conversion of the oxygen with the natural gas is carried out in the same environment as the endothermic steam reforming of the natural gas resulting in an enhanced energy efficient environment (see col. 7, lines 15–63).
U.S. Pat. No. 6,333,014 B1 to Filippi in a process arrangement for the co-production of ammonia and methanol, transfers energy from a hot stream by indirect heat exchange with another input stream; and,
U.S. Pat. No. 6,340,451 B1 to Pagani, et al. in a plant for the synthesis of ammonia and urea increases its output capacity by using a means for adjusting the various feed streams.
The methods disclosed above and their respective apparatuses are deficient in that none suggest carrying out the processing of methane or natural gas into ammonia in a limited environment that prevents the emission of greenhouse gases or utilizing the exothermic energy of one intermediate process enclosed in a reaction vessel to energize the endothermic energy consumption of a second intermediate process in said vessel and adjacent thereto for improved efficiency of production of ammonia. The importance of ammonia as a safe compound and carrier of hydrogen for fuel cells has been recognized in the new hydrogen fuel economy. Thus, the present invention fills the need for an energy efficient means to produce a safe hydrogen-containing compound, such as ammonia, from natural gas fields without harmful environmental effects.